This invention relates to trellis systems for vineyards or the like and more particularly to the attachment of horizontal trellis wires to vertical posts.
A typical vineyard arranged to be mechanically harvested will be planted so that there will be a plurality of parallel rows with spaced apart grape plants in each row. A trellis system is provided by installing a plurality of vertical posts along each row, usually a post at each plant and with an end post at each end of the row. One or more horizontal trellis wires are extended down each row anchored under tension to the end posts and attached to the intermediate posts. The vines are grown along the trellis wires which support the vines so that the grapes can be readily harvested therefrom.
The conventional manner of attaching the trellis wires to the intermediate wooden posts has been by the use of simple staples. In vineyards which are not mechanically harvested, this is a rapid, inexpensive and effective way of forming a trellis system. However, staple attachment has proven ineffective in keeping the wires attached to the posts when the vineyard is mechanically harvested, particularly when the harvester imparts a shaking action to the trellis. Such shaking often pulls the staples out of the posts, allowing the trellis wire to drop.
Another disadvantage of the staple attachment is encountered when a post is struck or a force imposed thereon in a direction along the length of the row. Since the staple attachment affords very little resistance to sliding movement of the attachment along the length of the trellis wire, such force will oftentimes push the post over and/or break it.
Attempts have been made to provide a more permanent attachment of a trellis wire to a post. For example, one manner is to form a wire loop around the trellis wire and the post and to twist the loop tightly and clamp the trellis wire against the post. This has proven to be a reasonably satisfactory expedient, although it still allows some sliding of the attachment along the length of the trellis wire. However, this manner of attachment is time consuming and, as a result, quite expensive.
Steel posts are often used, instead of wood posts, in vineyard trellis systems. Typically, the stake is notched to hold the trellis wire at a desired height above the ground and the trellis wire is held in the notch by means of a wire loop encircling the post and passing over the trellis wire. Again there is very little resistance to movement of the attachment along the length of the trellis wire and forces imposed on the post in a direction along the row can cause bending of the post and permanent deformation thereof. In addition, the post can twist about the vertical axis thereof and permanently deform when struck by the harvester since such trellis wire attachment provides no resistance to such twisting.